As health professionals with expertise in the links between air pollution and human health, we are
writing to express our grave concern about and opposition to the proposed plan to dispose of wood
debris on the Virgin Islands by burning them in air curtain incinerators.

Burning of brush and wood on St. Croix, St. Thomas and St. John will increase air pollution and therefore the risk of associated health problems, including exacerbation of asthma in children and adults; increased severity of chronic
obstructive pulmonary disease; and fatal myocardial infarction.

The alternative to burning—mulching and composting—is a far wiser choice on many levels. Mulching
and composting add essential nutrients to the soils of the islands which will increase overall soil health.
Mulching and composting avoid harmful exposures that pose health risks to people. And mulching and
composting will save money for the Virgin Islands now and in the future by avoiding the unnecessary
health care costs that will result from cardiac and respiratory illnesses produced by smoke exposure.
The authors of this letter include air pollution and wood smoke scientists who have published
extensively. Several of us have led international, national and regional assessments of the impacts of air
pollution, and wood smoke in particular, on human health. The authors include environmental and
occupational health scientists and practicing pediatricians with particular expertise in asthma and
neurodevelopment. Among us are long-term visitors to the Virgin Islands with strong connections to
island residents and the beautiful environment on which the regional economy depends.
Below we summarize the relevant scientific/medical literature and our assessment of the exposure and
health conditions in the Virgin Islands which form the basis for our concern. We cite over 30 peer
reviewed articles; the references are attached.

Relevant Scientific Literature
Decades of research on air pollution have established that fine particulate air pollution, a mixture of
solids and liquid droplets generated by combustion fuels including wood, is associated with significant
health effects. These include shortened life expectancy, as well as increases in specific health conditions
such as asthma attacks, heart attacks, stroke, chronic obstructive pulmonary disease, and a range of
other conditions, including neurological impairments (Grandjean P et al 2014; Kioumourtzoglou, MA et
al 2015). Air pollution and particulate matter specifically has been identified as a human carcinogen by
the International Agency for Research on Cancer (Straif 2013). There is evidence that short-term
exposure to particulate matter with the aerodynamic diameter of 2.5 microns or less–PM2.5–is
associated with stroke and heart failure as well as subclinical cardiovascular conditions such as systemic
inflammation, increased blood coagulation, increased blood pressure, and increased vascular
dysfunction (Brook RD et al, 2010). Numerous epidemiological studies examining the relationship
between increases in PM2.5 pollution and the most serious adverse health outcomes have not been able
to identify a “no risk” level of PM 2.5 (i.e. a no threshold model) (Pope III AC and Dockery DW, 2006 and
Book RD et al 2010). Fine particulates emitted into the outdoor ambient air pose an indoor as well as
outdoor air quality hazard (Allen R et al 2003; Larson T et al 2004).

In addition to PM2.5 particles, wood smoke also contains ultra-fine particles with an aerodynamic
diameter of less than 1 µm (Sippula O et al 2009). Both ultrafine and PM2.5 particles tend to deposit in
the deep lung where they can penetrate into the blood stream and can have systemic biological effects.
PM2.5 from wood biomass combustion can remain suspended in ambient air for longer periods of time,
can be transported over long distances, and can penetrate more readily into indoor environments as
compared to larger, coarser particles. (Wilson WE and Suh HH,al 1997)
Particulates are not the only pollutants of concern in emissions from wood burning. Wood smoke
contains many other hazardous substances which are known contributors to acute and chronic
illnesses, including asthma, cardiovascular disease, neurodevelopmental problems and cancer. These
include Carbon Monoxide, and Polycyclic Aromatic Hydrocarbons (PAHs). Some studies of PAHs have
found that wood combustion emits more carcinogenic PAHs per unit of fuel energy than several types of
coal (Oanh et al. 1999 ; Truesdale RS and Cleland JG 1982 ). Emissions from wood burning can also
include trace levels of heavy metals, such as arsenic, cadmium, and nickel which occur naturally in many
types of wood (Washington State Department of Ecology 2003 ; Demirbas 2008 ). While metals are not
a significant fraction of particulate pollution, one recent study of emissions from institutional and
commercial wood biomass combustion units found that heavy metals and trace elements showed a
tendency to concentrate in fine particles (Sippula et al. 2009 ). Burning “pressure-treated” wood is
highly hazardous.
Numerous studies show that exposure to wood smoke causes a range of acute and chronic health
problems, including harms to respiratory health in both children and adults, among them aggravation
of asthma and of chronic obstructive pulmonary disease, bronchitis, and decreased lung function
(Naeher et al, 2007; Boman BC, 2003). Two recent reviews add to the growing evidence of
cardiovascular impacts of wood smoke exposure (Reid CE, Brauer M et al, 2015; Sigsgaard T et al 2015).
One study documents a clear link between exposure to wood smoke and increased hospitalizations for
heart attacks (Weichenthal S et al 2017). Studies have also identified additional health risks for young
children, notably an increased risk of bronchiolitis—the leading cause of hospitalizations for children
under one year old—among those exposed to the highest levels of wood smoke compared to those
exposed to the lowest levels (Karr CJ et al 2009).
The scientific literature also establishes that individuals already burdened by significant
environmental, social and economic stressors are more likely to be adversely affected by exposure to
air pollution (Pope and Dockery 2006 ; Brook et al. 2010 ; Johnson PR and Graham JJ, 2005; Landrigan
1998 ). While not all of these populations have been studied with respect to wood smoke exposure,
there is evidence as noted above that children as well as people with existing respiratory illness are
particularly susceptible to the adverse effects of wood smoke (Naeher et al 2007 ).

Exposure and Health Considerations in the Virgin Islands
The level of risk to people’s health from wood burning depends on factors related to the conditions of
burning, and factors related to people. Several of these increase the likelihood that the proposed
wood burning will harm the health of people in the Virgin Islands.
First, air curtain incinerators do not allow for high-temperature nor complete or efficient burning,
which increases emissions of hazardous compounds. (Johansson et al 2004) Yet regardless of the
method, burning wood debris left over from the hurricanes in the VI would generate higher hazard
emissions because of physical and chemical properties of the wood. These include moisture content
(Bignal KL et al 2008; Atkins A et al 2010), the variability in size and composition of wood debris, and
the large amount of bark and roots, all of which contribute to incomplete combustion, higher levels of
emissions and higher toxicity of particles. (Demirbas 2008 ; Beauchemin PA and Tampier M, 2008 ). In
addition, some of the wood has likely been in contact with seawater, in which case dioxin emissions are
possible (Lavric ED et al, 2004). Finally, burning brush and wood from poisonous trees, such as the
Machineel, found in the Virgin Islands, can cause severe irritation of the eyes and skin (Brittanica
Editors, accessed 2017) and likely the lungs as well (NIOSH accessed 2017).
On all three Virgin Islands, people of all ages from young infants to the very old live, work and play near
where the burning will take place, increasing the risk of health problems. The percentage of pollution
that is inhaled relative to the overall volume of emissions—known as the “intake fraction”—is higher the
closer populations are to the source. The intake fraction can also increase when respiration rates are
higher than normal, such as when people are exercising (Hoppin P and Jacobs M, 2012). Workers
directly involved in the burning would be at particular risk for health problems (Youssouf H et al 2014;
Hoppin P and Jacobs M, 2013).

The health risks from wood burning also need to be considered in the context of the high vulnerability
and susceptibility of people on the Islands at this time.

People in the Virgin Islands suffer disproportionately from a range of health conditions (Callwood et al
2012) which make them more likely to be affected by lower levels of pollutant concentrations. In
addition, some sub-populations are inherently more susceptible to health effects because of their age or
condition—in particular pregnant women, infants, children and the elderly.
Health hazards abound during this hurricane recovery period. Exposure to diesel from generators;
mold from infiltration of water into damaged buildings; high levels of dirt and dust indoors and
outdoors; stress caused by the immediate experience of the storms and the hardships that have ensued,
including lack of basic services and loss of livelihoods as well as poor economic prospects going
forward—all these are risk factors for acute and chronic health conditions. Interactions among these
risk factors can increase the risk of both disease exacerbation and onset; for example, the combined
exposures of vehicle emissions and psychosocial stress can have a multiplicative impact on lung function
in children exposed to both (Wright 2011). It would be irresponsible to intentionally introduce
additional environmental exposures to the people of the Virgin Islands at this time, especially when
non-polluting alternatives exist.

In conclusion, the robust scientific literature on the health hazards of wood smoke and the current
conditions in the Virgin Islands—including the range of environmental and social risk factors to which
people are currently exposed–provide the basis for our professional opinion that burning wood debris
from the hurricanes poses unnecessary risks to human health. We strongly recommend that you do
everything in your power to prevent burning of wood and brush debris, either in air curtain
incinerators or otherwise.
We understand that public policy decisions often require trade-offs. In this case, we believe that a
decision to burn virgin wood debris is unacceptable, both because of the risks we describe, and
because of the feasibility of the much safer alternative of mulching and composting. To the extent
that costs are central in the debate, we urge that you consider the increased health care costs
associated with acute and chronic health impacts, as well as the long-term economic benefits of the
Virgin Islands serving as a beacon for the region, indeed for the globe, in demonstrating policies and
practices that both protect human health and establish sustainable infrastructure for the future.
Sincerely,
Polly Hoppin, ScD, Research Professor, University of Massachusetts Lowell and Program Director,
Environmental Health, Lowell Center for Sustainable Production (Also Convenor, Northeast Regional
Initiative on Wood Biomass and Health)*
Nicholas A. Ashford, PhD., JD, Professor of Technology and Policy and Director, MIT Technology & Law
Program
Michael Brauer, ScD, The University of British Columbia (also National Academy of Medicine (U.S):
Standing Committee on the Medical and Epidemiological Aspects of Air Pollution on U.S. Government
Employees and their Families (2017 – ); World Health Organization, Guideline Development Group: WHO
Global Air Quality Guidelines (2016 – ); Global Burden of Disease. Member, Core Analytic Team. (2013- ))
Catherine Chapman, MD, practicing pediatric neurologist, Boston Children’s Hospital
Richard Clapp, D.Sc, Professor Emeritus, Department of Environmental Health, Boston University School
of Public Health
David Kriebel, ScD, Professor, University of Massachusetts Lowell
Philip J Landrigan, MD, MSc, FAAP. Dean for Global Health, and Professor of Preventive Medicine and
Pediatrics, Icahn School of Medicine at Mount Sinai (Also Co-Chairman, The Lancet Commission on
Pollution and Health)
Shari Nethersole, MD, practicing pediatrician and Executive Director for Community Health, Boston
Children’s Hospital